The SuperCollider 3 Synth Server is a simple but powerful synthesis engine. While synthesis is running, new modules can be created, destroyed and repatched, sample buffers can be created and reallocated. Effects processes can be created and patched into a signal flow dynamically at scheduled times.All running modules are ordered in a tree of nodes that define an order of execution. Patching between modules is done through global audio and control buses.

All commands are received via TCP or UDP using a simplified version of Open Sound Control (OSC). The synth server and its client(s) may be on the same machine or across a network. The synth server does not send or receive MIDI. It is expected that the client will send all control commands. If MIDI is desired, it is up to the client to receive it and convert it to appropriate OSC commands for the synth engine.

Synth definitions are stored in files generated by the SuperCollider language application. Unit generator definitions are Mach-O bundles (not to be confused with CFBundles). The Unit generator API is a simple C interface.

Main Design Concepts

Node

A Node is an addressable node in a tree of nodes run by the synth engine. There are two types, Synths and Groups. The tree defines the order of execution of all Synths. All nodes have an integer ID.

Group

A Group is a collection of Nodes represented as a linked list. A new Node may be added to the head or tail of the group. The Nodes within a Group may be controlled together. The Nodes in a Group may be both Synths and other Groups. At startup there is a top level group with an ID of zero that defines the root of the tree. If the server was booted from within SCLang (as opposed to from the command line) there will also be a 'default group' with an ID of 1 which is the default target for all new Nodes. See RootNode and default_group for more info.

Synth

A Synth is a collection of unit generators that run together. They can be addressed and controlled by commands to the synthesis engine. They read input and write output to global audio and control buses. Synths can have their own local controls that are set via commands to the server.

Synth Definition

Synths are created from Synth Definitions. Synth Definition files are created by the SuperCollider language application and are loaded into the synth server. Synth Definitions are referred to by name.

Audio Buses

Synths send audio signals to each other via a single global array of audio buses.Audio buses are indexed by integers beginning with zero. Using buses rather than connecting synths to each other directly allows synths to connect themselves to the community of other synths without having to know anything about them specifically. The lowest numbered buses get written to the audio hardware outputs. Immediately following the output buses are the input buses, read from the audio hardware inputs. The number of bus channels defined as inputs and outputs do not have to match that of the hardware.

Control Buses

Synths can send control signals to each other via a single global array of control buses.Buses are indexed by integers beginning with zero.

Shared Control Buses

The internal server (which runs within the same address space as the client app) also has a number of shared control buses to which the client app has synchronous read/write access.These buses are indexed by integers beginning with zero.

Buffers

Buffers are arrays of 32 bit floating point values with a small descriptive header. Buffers are stored in a single global array indexed by integers beginning with zero. Buffers may be safely allocated, loaded and freed while synthesis is running, even while unit generators are using them. Buffers are used for wave tables, sample buffers, delay lines, envelopes, or for any other need which can use an array of floating point values. Sound files may be loaded into or written from buffers.

Unit Generator Definitions

Unit Generator Definitions are plug-ins loaded automatically when the program starts. They are binary code libraries that are used as building blocks by Synths to build synthesis algorithms. Unit Generator Definitions have names that match the names of SuperCollider language classes used in building Synth Definitions.

Command Line Arguments

One of -u or -t must be supplied. Both may be supplied.

-u udp-port-number

a port number 0-65535.

-t tcp-port-number

a port number 0-65535

-v verbosity

Controls the verbosity of server messages. A value of 0 is normal behaviour, -1 suppresses informational

Messages are similar in format to Open Sound Control messages, except that OSC #bundles may not be nested, and pattern matching of the command name is not performed. When streamed via TCP, Messages are each preceeded by a 32 bit integer giving the length in bytes of the message. UDP datagrams contain this length information already.